[Mesa-users] convergence problem

Tue May 14 10:18:45 EDT 2019

On Tue, May 14, 2019, 08:57 sheyda najafi <sh.najafi8590 at gmail.com> wrote:

> Dear Pablo
>
> Thank you very much.
>
> I thought that by adding the new acceleration as extra_dpdm in HSE
> equation of MESA code, other equations which depend on acceleration,
> change due to gravitational force + extra force.
>
> 1)So there is no relation that relates grav to extra_dpdm or dlnp_dm_qhse?
>

That scale height is derived from the standard eqn for hydrostatic
equilibrium

dP/dr = -rho g

Where grav is just the standard gravity. In your case, you could write your
equations in dP/dr form and get the value for the scale height as well.

2)what might happen to the star if I add extra_dpdm to HSE equation
> and do not change pressure_scale_height?
>

The scale height is mostly used for convective energy transport as well for
overshooting.

3)Do you think it would have impact on stability of the star?
>

Would not expect to affect stability at all. If you're thinking about this
in terms of making non-working simulations work I would not recommend it.

Cheers

> Thank you
> Sheyda
>
> On 5/14/19, Pablo Marchant <pamarca at gmail.com> wrote:
> > Hi Sheyda,
> >
> > The pressure scale height is set in star/private/mlt_info.f90, assuming
> > standard hydrostatic equilibrium, so its set as
> >
> > scale_height = P / (grav*rho)
> >
> > If you want to modify the pressure scale height then you'll have to
> adjust
> > this accordingly. You can reimplement mlt using the other_mlt hook, just
> > copy all what's neccesary from mlt_info into your run_star_extras and
> > adjust the line above. Note that you also have to set properly the
> partial
> > derivatives for the scale height, which are required by the newton
> solver,
> > this is currently done in mlt_info in this way
> >
> > d_scale_height_dvb = scale_height*(dP_dvb/P - d_grav_dvb/grav -
> > dRho_dvb/Rho)
> >
> > Here the variables denoted as *_dvb are arrays containing the partial
> > derivatives with respect to each variable. You should be able to figure
> out
> > how itworks by digging a bit in mlt_info. From your modifications, you'll
> > need to figure out how to get the partial derivatives for dphi with
> respext
> > to the structure variables.
> >
> > Cheers
> >
> > On Tue, May 14, 2019, 07:06 sheyda najafi via Mesa-users <
> > mesa-users at lists.mesastar.org> wrote:
> >
> >> Dear MESA users
> >>
> >> I have changed extra_dpdm to add a new acceleration term to HSE
> >> equation in MESA code.
> >> (p(i-1)- p(i))/dm_bar(i)=( -standard_cgrav*m(r))/(4*pi* s% r(i)**4) -
> >> beta*(clight**2) *rho_face(i) (dphi/dm_bar)
> >> therefore
> >> extra_dpdm(i)= - beta*(clight**2) *rho_face(i) dphi/dm_bar
> >>
> >> which i have asked about the quantities and the shape of this new term
> >> in previous emails.
> >>
> >>  My question is how does this extra acceleration change the pressure
> >> scale height in the code. I can not find the relation. I know that
> >> pressure scale height depends on p_face and rho_face and grav. The
> >> extra_dpdm has impact on density and pressure but I can not find the
> >> relation between grav and extra_dpdm in the code.
> >>
> >> Thank you very much
> >> Sheyda Najafi
> >>
> >> On 5/7/19, sheyda najafi <sh.najafi8590 at gmail.com> wrote:
> >> > Dear Mesa users
> >> >
> >> > I have another question regarding my previous emails.
> >> >
> >> > As i  said I wanted to study the evolution of 1 solar mass star in the
> >> > presence of
> >> > new extra acceleration term :(-beta*(clight**2)*(dphi/dr)).
> >> >  i have changed the
> >> > extra_dPdm subroutine of MESA code to add
> >> > the extra term (-beta*rho(clight**2)*(dphi/dm)) ==>( in lagrangian
> >> > framework) .
> >> >  where phi depends on local density of each layer(cell density: s%
> >> > rho).
> >> >  which is named (xn) in the code. and beta is a constant.
> >> > i have added the extra term as follows
> >> >
> >> >            do k = 1,2
> >> >              s% extra_dPdm(k) = -( ((   xn(k)-    xn(k+1))/(s%
> >> > dm_bar(k+1)))*((beta*(clight**(2.0d0)))*(s% rho_face(k))) )
> >> >
> >> >          end do
> >> >
> >> >          do k = 2, s% nz-1
> >> >           s% extra_dPdm(k) = -( (((   xn(k)-    xn(k+1))/(s%
> >> dm_bar(k+1)))+
> >> > &
> >> >          ((   xn(k-1) -   xn(k))/(s% dm_bar(k))))
> >> > *((beta*(clight**(2.0d0)))*(s% rho_face(k))*(1.d0/2.d0)) )
> >> >
> >> >          end do
> >> >
> >> >          do k = s% nz-1, s% nz
> >> >           s% extra_dPdm(k) = -( ((   xn(k-1) -    xn(k))/(s%
> >> > dm_bar(k)))*((beta*(clight**(2.0d0)))*(s% rho_face(k))) )
> >> >
> >> >         end do
> >> >
> >> > I noticed that  s% dm_bar(s%nz) = s%dm(s% nz) + s%dm(s%nz-1)/2
> >> > and not (s% dm(s% nz) + s% dm(s%nz-1))/2.
> >> >
> >> > i am not sure that dm_bar must be used in extra_dpdm or  (s% dm(s% nz)
> >> > + s% dm(s%nz-1))/2.
> >> >
> >> > Thank you very much
> >> > Sheyda Najafi
> >> >
> >> >
> >> > On 10/21/18, sheyda najafi <sh.najafi8590 at gmail.com> wrote:
> >> >> Dear Josiah and MESA users
> >> >>
> >> >>
> >> >> I have another question regarding my previous emails. i have asked it
> >> >> before but unfortunately no one answered.
> >> >>
> >> >> As i  said I wanted to study the evolution of 1 solar mass star in
> the
> >> >> presence of
> >> >> new extra acceleration term :(-beta*(clight**2)*(dphi/dr)).
> >> >>  i have changed the
> >> >> extra_dPdm subroutine of MESA code to add
> >> >> the extra term (-beta*rho(clight**2)*(dphi/dm)) ==>( in lagrangian
> >> >> framework) .
> >> >>  where phi depends on local density of each layer(cell density: s%
> >> >> rho).
> >> >>  which is named (xn) in the code. and beta is a constant.
> >> >>
> >> >>            do k = 1,2
> >> >>              s% extra_dPdm(k) = -( ((   xn(k)-    xn(k+1))/(s%
> >> >> dm_bar(k+1)))*((beta*(clight**(2.0d0)))*(s% rho_face(k))) )
> >> >>
> >> >>          end do
> >> >>
> >> >>          do k = 2, s% nz-1
> >> >>           s% extra_dPdm(k) = -( (((   xn(k)-    xn(k+1))/(s%
> >> >> dm_bar(k+1)))+
> >> >> &
> >> >>          ((   xn(k-1) -   xn(k))/(s% dm_bar(k))))
> >> >> *((beta*(clight**(2.0d0)))*(s% rho_face(k))*(1.d0/2.d0)) )
> >> >>
> >> >>          end do
> >> >>
> >> >>          do k = s% nz-1, s% nz
> >> >>           s% extra_dPdm(k) = -( ((   xn(k-1) -    xn(k))/(s%
> >> >> dm_bar(k)))*((beta*(clight**(2.0d0)))*(s% rho_face(k))) )
> >> >>
> >> >>         end do
> >> >>
> >> >> Since i did not know the value of s%rho(0) i did'nt have xn(0) to
> >> >> write extra_dpdm it in 1 part therefore i have split it in three
> >> >> parts. how it is possible to write this term in 1 part. i mean if i
> >> >> want to write the extra term as :
> >> >>
> >> >>          do k = 1, s% nz
> >> >> s% extra_dpdm(k)= -((   xn(k-1)-    xn(k)) / s% dm_bar(k)) * beta*
> >> >> (clight**2)* ( s%rho_face(k)).
> >> >>         end do
> >> >>
> >> >> I will have problem in finding the value of xn(0). because xn is
> >> >> related to cell density s%rho(0) via
> >> >>
> >> >>    xn(i)= (( n1*(lambda**(4.d0+n1)) )/(((mpl)**(n1))*clight*beta*s%
> >> >> rho(i)))**(1.d0/(n1+1.d0))
> >> >>
> >> >> lambda, mpl, n1 and beta are constant.
> >> >>
> >> >>  which density should i use as rho(0) ??
> >> >>
> >> >> (for your kindly information my codes are attached in the email)
> >> >> Thank you in advance
> >> >>
> >> >>
> >> >> Sheyda
> >> >>
> >> >
> >> _______________________________________________
> >> mesa-users at lists.mesastar.org
> >> https://lists.mesastar.org/mailman/listinfo/mesa-users
> >>
> >>
> >
>
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